The present disclosure is related to electrically conductive attachment devices and racks for supporting articles to be coated.
Racks for supporting articles or workpieces to be coated are common to many finishing systems. In the past, such support racks have usually included several vertically stacked, horizontal rows or tiers of protruding, article engaging hooks upon which workers would hang workpieces for surface coating. A variety of coating techniques have been commonly employed such as spray coating, dip coating, and plating. These coating techniques often require the articles to be electrically charged or grounded to attract oppositely charged particles of a coating or plating material causing the material to adhere to the surface of the articles. These coating techniques are also commonly referred to as electro-static, electro-deposition, or electro-plating.
The article engaging hooks used with article support racks are often connected to vertically spaced, horizontal cross-bars. The cross-bars are in turn connected at their opposite ends to vertical side bars. The side bars bear the weight of the cross-bars and in the articles to be coated.
Many industrial finishing systems include a conveyor from which one or more article support racks are suspended. Typically, the conveyor provides an electrical connection and the electrical conductivity through the support rack to the article engaging hooks enables the articles to be electrically charged or electrically grounded as required by the finishing system. The conveyors have also provided for the transportation of support racks through the finishing system.
In many applications, a large number of workpieces, such as component parts, are mounted on the hooks for transportation through a finishing system. Many finishing systems have a series of stations at which the workpieces may be sequentially treated by applying one or more materials for cleaning, rinsing, surface preparation, drying, coating, curing or baking the workpieces. For example, in electro-static systems, liquid or solid charged particles have been sprayed onto the workpieces at a coating station such as a spray booth. In order for the charged particles to be attracted to the workpieces, a conductive path from the conveyor through the support rack to the workpiece is required. Similarly, in electro-deposition systems, liquid or solid particles of coating material may be suspended in a solution and the workpieces on a support rack may be dipped into a vat of this solution at a different coating station. Many plating operations operate in a similar manner.
The finishing systems are typically designed to finish or coat a large number of identical parts. Often, the finishing systems have been used for only one size part at a time, processing all parts of one size and then coating parts of a different size. One obstacle to efficient operation of finishing systems has been that workpieces come in different sizes and with different support requirements. In the past, it has been necessary to utilize a different support rack for each job or to disassemble and reassemble the support racks into different configurations when transitioning between different size workpieces. The productivity of a finishing system is determined, in part, by the number of workpieces that may be coated at one time, therefore support racks have often been customized to specific size parts. As each support rack was tailored to a specific size or type of part, multiple support racks were required significantly increasing the cost and space requirements of the finishing system.
To overcome the inefficiencies of using different sets of permanently configured support racks, racks that may be disassembled and reconfigured have been desired. If such racks can be reconfigured without excessive time or labor costs and will operate properly once reconfigured, the efficiency and productivity of a finishing system may be improved. Such racks permit many diverse and different parts to be finished, yet require an investment in only one set of racks.
Various reconfigurable support racks have been proposed. However, the development of a single, reconfigurable set of racks has posed several problems resulting from the fact that finishing or coating material often adheres not only on the workpieces, but also on the portions of the support rack exposed during the finishing process. Paint or other coating material ordinarily has a high electrical resistance. Consequently, when a support rack that has been coated with a coating material during previous finishing operations is disassembled and reassembled, the coating material often prevents or degrades electrical contact between the component parts of the rack. This problem is especially difficult in dip coating or electro-deposition coating systems because when the support rack is immersed in a coating material all surfaces of the support rack are susceptible to the accumulation of undesired coating material. Additionally, techniques, such as shields or covers, adapted for preventing spray coatings from accumulating have sometimes created pockets in which coating material accumulates during dip coating further interfering with the reconfiguration of the support racks.
When prior support racks have become coated with excess coating material, one solution has been to chemically clean or strip the coating material from the support rack. These cleaning or stripping operations often require removing the support rack from the finishing system decreasing the productivity of the finishing system and increasing costs. Another problem with some previously proposed adjustable support racks is the limited range of adjustment or interchangeability of the support rack components. For example, some prior support racks (see, e.g., U.S. Pat. No. 4,872,963) provided custom cross-bars adapted for use with a single rack. Another frequently encountered problem with previous designs has been that accumulated coating material often mechanically bonds the component parts of a support rack, can hinder the disassembly, and can mechanically interfere with reassembly of the support rack in a different configuration.
In light of the limitations of the previously available systems, therefore, there continues to be a need for article support racks and attachment systems capable of being reconfigured while maintaining an electrical connection to the articles and reducing the time and cost of disassembling and reassembling the support rack to accommodate articles of different size or configurations.
An electrically conductive attachment system is disclosed comprising (a) a tubular portion of electrically conductive material adapted to be attached to a support beam having (i) a top opening and a bottom opening, and (ii) an inner surface extending substantially between the top opening and the bottom opening; and (b) a mounting clip adapted to be attached to a cross-bar and to releaseably engage the tubular portion having (i) an attachment portion adapted to electrically connect the mounting clip to the cross-bar, and (ii) an engagement portion adapted to be inserted through the top opening of the tubular portion engaging the inner surface of the tubular portion and providing an electrical connection between the tubular portion and the mounting clip; and (c) the attachment system capable of releaseably connecting the cross-bar substantially transverse the support beam and providing an electrical connection therebetween.
Also disclosed is the tubular portion having a substantially circular cross-section or a substantially rectangular cross section. The tubular portion may have a non-circular cross-section including at least two corners. The engagement portion may be adapted to engage the inner surface of the tubular portion substantially adjacent at least two corners of the tubular portion or substantially adjacent four corners of the tubular section. In one example, the tubular portion may comprise steel square tube.
Also disclosed is that the attachment portion of the mounting clip may comprise a torsion spring, a resilient wire, or a resilient wire extending around the cross-bar. The engagement portion of the mounting clip may comprise a resilient wire forming a substantially J-shaped hook adapted to resiliently engage the inner surface of the tubular portion. The engagement portion may be further adapted to abrade the inner surface of the tubular portion during insertion of the engagement portion into the tubular portion.
An electrically conductive article support rack is also disclosed comprising (a) a hanger portion; (b) two support beams electrically connected to the hanger portion adapted to support at least one cross-bar transverse the support beams; (c) the at least one cross-bar adapted to support articles in electrical connection with the support rack, the cross-bar being attached to the support beams by attachment devices; (d) the attachment devices each comprising (1) a tubular portion of electrically conductive material adapted to be attached to a support beam having (i) a top opening and a bottom opening, and (ii) an inner surface extending substantially between the top opening and the bottom opening; and (2) a mounting clip adapted to be attached to a cross-bar and to releaseably engage the tubular portion having: (i) an attachment portion adapted to electrically connect the mounting clip to the cross-bar; and (ii) an engagement portion adapted to be inserted through the top opening of the tubular portion engaging the inner surface of the tubular portion and providing an electrical connection between the tubular portion and the mounting clip; and (3) the attachment devices capable of releaseably connecting the cross-bar substantially transverse the support beams and providing an electrical connection therebetween.
An alternative electrically conductive article support rack is also disclosed comprising (a) a hanger portion; (b) two vertical support beams electrically connected to the hanger portion adapted to support at least one cross-bar transverse the vertical support beams, (c) the at least one cross-bar adapted to support articles in electrical connection with the support rack, the cross-bar being attached to the vertical support beams by attachment devices, (d) the attachment devices each comprising (1) a tubular portion of electrically conductive material adapted to be attached to a support beam having (i) a top opening and a bottom opening; (ii) an inner surface extending substantially between the top opening and the bottom opening; and (iii) a non-circular cross section including at least two corners; and (2) a mounting clip adapted to be attached to a cross-bar and to releaseably engage the tubular portion having (i) a torsion spring attaching the mounting clip to a cross-bar; and (ii) a wire-form engagement spring adapted to be inserted through the top opening of the tubular portion resiliently engaging the tubular portion substantially adjacent opposite corners of the tubular portion and providing an electrical connection between the mounting clip and the tubular portion; and (3) the attachment device capable of releaseably connecting the cross-bar substantially transverse to the vertical support beams and capable of providing an electrical connection therebetween.
Also disclosed is a cross-bar comprising end portions connected to opposite ends of a center portion, where the end portions are adapted to receive the torsion spring of the mounting clip. The end portions of the cross-bar may comprise stainless steel rod.